Last summer, Montrezl Harrell was scrolling through his Instagram feed when he saw a highlight video of NBA players scrimmaging.

During the clip, Harrell noticed New Orleans Pelicans guard Jrue Holiday was wearing a tie-back headband.

“That was really the first place I saw it,” Harrell told The Athletic.

Harrell, who started wearing a headband at Louisville as he grew his hair out, liked the aesthetics of the look. He just wasn’t sure if the NBA would approve of him swapping out the league’s regular getup for a karate-style headband.

At the beginning of the 2018-19 season, Harrell asked the Clippers’ managers of team operations, Kyle Rohde and Max Reza, if he could wear the NikeCourt Dri-FIT 2.0 tennis head tie instead of a league-issued Nike headband. Rohde and Reza told Harrell they needed the league’s approval first.

After seeing Holiday wear the head tie in the preseason and the beginning of the regular season, and confirming...